Why do my unwrapped UVs appear outside of the UV canvas?
It appears that something went wrong in a proccess of your unwrapping since there is that line that take up all the space in your grid. Maybe missed some seems? Though, for a sword blade i would use project from view

It also appears that tou havent applied the scale for you mesh. If you ever rescale, rotate or move around your object (in object mode i believe), you have to press CTRL+A while you have your object selected in object mode and select one of the options you need.

If you are unsure what you have changed, while having your cursor inside the 3D View area (where you can see your objects basically), press N and in the window that came out of the right side, check if the locations and rotations are all set to 0 and if the scales are all set to 1. If they are not, that means you have been transforming your objects without applying the changes